imgtools problem

Once again I will pose the question: Why is it that Imgtool fails to create an image of the whole file on some occasions?

IEANIC_ROOM worked fine. Same procedure for RESIDENT_EVIL, Imgtool only creates .img for VIDEO_TS.VOB and not any of the other. VOBs. And, both movies are by Tri-Star/Columbia. I must conclude that Imgtool is not reliable. ??